Obama has agreed to withdraw ALL US troops from Iraq, leaving only an Embassy guard. The original plan was to leave a few thousand men to train the Iraqi forces and deter an invasion from Iran. The Iranians know that we would like to stop their nuclear weapons program and do a little catchup for the embassy invasion of 20 years ago. They would think twice, maybe three times before marching into Iraq and getting in a shooting incident with the Americans. 'Cause for all they know the Americans are looking for a good excuse to bomb their nuclear program to bits.
Anyhow, the Iraqi's are on their own now. And they don't have any reliable American troops to take care of any little domestic problems, like Moctadar Al-Sadr, who might need dealing with. And once out, it will take another 9-11 to get the US to send troops back there.
Was it me, I would have bargained a little harder with the Iraqis about an acceptable status of forces agreement. But Obama doesn't listen to anyone, let alone little old me.